Problem: $ { \left[\begin{array}{r}{1} \\ {-2} \\ {1}\end{array}\right]-\left[\begin{array}{r}{0} \\ {-2} \\ {2}\end{array}\right] = {?} } $
Answer: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{r}{1}-{0} \\ {-2}-{-2} \\ {1}-{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{1} \\ {0} \\ {-1}\end{array}\right]}$